<%@ page contentType="image/jpeg; charset=UTF-8" %>
<%@ page import="java.awt.*"%>
<%@ page import="java.awt.image.*"%>
<%@ page import="java.util.*"%>
<%@ page import="javax.imageio.*"%>

<%!
	Color getRandColor(int fc, int bc) {
		// 给定范围获得随机颜色
		Random random = new Random();
		if (fc > 255)
			fc = 255;
		if (bc > 255)
			bc = 255;
		int r = fc + random.nextInt(bc - fc);
		int g = fc + random.nextInt(bc - fc);
		int b = fc + random.nextInt(bc - fc);
		return new Color(r, g, b);
	}
%>
<%
	// 设置页面不缓存
	response.setHeader("Pragma", "No-cache");
	response.setHeader("Cache-Control", "no-cache");
	response.setDateHeader("Expires", 0);

	// 在内存中创建图象
	int width = 60, height = 20;
	BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);

	// 获取图形上下文
	Graphics g = image.getGraphics();

	// 生成随机类
	Random random = new Random();

	// 设定背景色
	//g.setColor(getRandColor(200, 250));
	g.setColor(new Color(56, 58, 76));
	g.fillRect(0, 0, width, height);

	// 设定字体
	g.setFont(new Font("Times New Roman", Font.PLAIN, 18));

	// 画边框
	//g.setColor(new Color());
	//g.drawRect(0,0,width-1,height-1);

	// 随机产生15条干扰线，使图象中的认证码不易被其它程序探测到
	//g.setColor(getRandColor(160, 200));
	/*
	for (int i = 0; i < 10; i++) {
		int x = random.nextInt(width);
		int y = random.nextInt(height);
		int xl = random.nextInt(12);
		int yl = random.nextInt(12);
		g.drawLine(x, y, x + xl, y + yl);
	}
	*/
	String randstring = "0123456789";

	// 取随机产生的认证码(4位数字)
	String sRand = "";
	for (int i = 0; i < 4; i++) {
		String rand = String.valueOf(String.valueOf(randstring.charAt(random.nextInt(10))));
		//String.valueOf(random.nextInt(10));
		sRand += rand;
		// 将认证码显示到图象中
		//g.setColor(new Color(20 + random.nextInt(110), 20 + random.nextInt(110), 20 + random.nextInt(110)));
		//设置验证码的颜色为白色
		g.setColor(new Color(255, 255, 255));
		// 调用函数出来的颜色相同，可能是因为种子太接近，所以只能直接生成
		g.drawString(rand, 13 * i + 6, 16);
	}

	// 将认证码存入SESSION
	session.setAttribute("rand", sRand);

	// 图象生效
	g.dispose();

	// 输出图象到页面
	try {
		response.reset();//在weblogic下面部署时，出现验证码无法显示的问题，后台报错，加上这句话就解决问题了。
		ImageIO.write(image, "JPEG", response.getOutputStream());
		out.clear();
		out = pageContext.pushBody();
	} catch (Exception e) {
		e.printStackTrace();
	}
%>